Supercritical fluid technology for cleaning processing chambers and systems

ABSTRACT

The invention includes a method of cleaning a processing chamber by introducing supercritical fluid into the processing chamber. A residue over an internal chamber surface is contacted with the supercritical fluid to remove the residue from the surface. The invention also includes a method of removing deposited material from internal surfaces of a processing system. A cleaning agent comprising carbon dioxide is provided in liquid phase or supercritical phase into at least a portion of the processing system. A material deposited on an internal surface of the processing system is contacted with the cleaning agent to solubilize at least a portion of the deposited material and the solubilized fraction is removed from the system. The invention further includes a processing system which includes a supercritical fluid source in selective fluid communication with a processing chamber configured to selectively flow supercritical fluid into the chamber during a chamber cleaning process.

RELATED PATENT DATA

This patent resulted from a divisional application of U.S. patentapplication Ser. No. 10/636,028, filed Aug. 6, 2003.

TECHNICAL FIELD

The invention pertains to methods of cleaning a processing chamber. Inparticular applications, the invention pertains to methods of cleaningsemiconductor processing chambers using a supercritical fluid. Theinvention also pertains to removing deposited material from internalsurfaces of processing systems. The invention further pertains to aprocessing system.

BACKGROUND OF THE INVENTION

A variety of systems are utilized in materials processing andfabrication technologies such as, for example, semiconductor processing.Exemplary processing systems include deposition systems such as varioustypes of physical vapor deposition systems, chemical vapor depositionsystems, furnaces, etc. Many of these systems include one or moreprocessing chambers, various processing equipment and processing tools,associated interconnects, feed and/or exhaust lines, and other systemcomponents that may become contaminated during a processing event. Suchcontamination can be due to formation of residue materials such as oneor more reagent, product or byproduct involved in or produced by theprocessing event. The presence of residue material on internal surfacesof the processing system can affect processing efficiency or precision,and can in some instances result in contamination of the material ordevice being processed.

Conventional system cleaning techniques often utilize a solvent orsolvent system that is expensive, environmentally unfriendly, and/orinefficient. In some instances, systems are configured to includespecial components such as heated lines and/or cold traps in an attemptto reduce contamination of system components or surfaces by residuematerials. Additionally, due to the intricate nature of many processingtools, equipment and internal regions of various processing systems,some areas are not highly accessible to conventional solvents, othercleaning agents or alternative techniques. Accordingly, conventionalcleaning methods can be cost prohibitive and unreliable.

It would be desirable to develop alternative methods for cleaningprocessing systems, system components and associated tools andequipment.

SUMMARY OF THE INVENTION

In one aspect the invention encompasses a method of cleaning aprocessing chamber. A supercritical fluid is provided into a processingchamber which has a residue material over at least one internal chambersurface. The residue material is contacted with the supercritical fluidto remove at least some of the residue from the internal surface.

In one aspect the invention encompasses a method of removing depositedmaterial from internal surfaces of a processing system. A cleaning agentcomprising carbon dioxide is provided into at least a portion of theprocessing system. The carbon dioxide can be provided in liquid phase orsupercritical phase. A material deposited on an internal surface of atleast a portion of the processing system is contacted with the cleaningagent to solubilize at least a portion of the deposited material. Thesolubilized fraction is subsequently removed from the system.

In one aspect, the invention encompasses a processing system whichincludes a supercritical fluid source in selective fluid communicationwith a processing chamber. The system is configured to selectively flowsupercritical fluid into the chamber during a chamber cleaning process.The system also contains a recovery vessel in fluid communication withthe processing chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic, cross-sectional view of an exemplary apparatussystem which can be subjected to cleaning methodology of the presentinvention.

FIG. 2 is a diagrammatic, cross-sectional view of a portion of thesystem shown in FIG. 1 at a preliminary processing stage of a method ofthe present invention.

FIG. 3 is a view of the FIG. 1 system portion shown at a processingstage subsequent to that of FIG. 2.

FIG. 4 is a diagrammatic, cross-sectional view of a second exemplaryfragment of system 10 shown in FIG. 1, at a preliminary processing stageof a method of the present invention.

FIG. 5 is a view of the FIG. 4 system fragment shown at a processingstage subsequent to that of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

In particular applications, the invention encompasses a process ofcleaning one or more surfaces of semiconductor processing systems. Thecleaning process can include exposing a surface of the processing systemto a supercritical fluid. As is known to persons of ordinary skill inthe art, a supercritical fluid is defined as any substance that is aboveits critical temperature (T_(c)) and critical pressure (P_(c)). T_(c) isthe highest temperature at which a gas can be converted to a liquid byan increase in pressure, and P_(c) is the highest pressure at which aliquid can be converted to a traditional gas by an increase in thetemperature of the liquid. The critical region for a particularsubstance is the region on a phase diagram for a given substance whereboth temperature and pressure are at or above their correspondingcritical values.

In the critical region, a substance exists in a single phase whichpossesses properties of both a gas and a liquid. Supercritical fluidsdiffer from traditional liquids in several aspects. For example, thesolvent power of a supercritical fluid will typically increase withdensity at a given temperature. Additionally, supercritical fluids havevery low effective viscosity and surface tension allowing penetrationinto very small areas and features. In particular applications, thecleaning processes of the invention can utilize a liquid cleaning agentthat is near the critical point of the agent. When a liquid cleaningagent is utilized, the liquid can preferably be at a temperature greaterthan or equal to about 90% of T_(c) and at a pressure greater than orequal to about 90% of P_(c). More preferably, when a liquid cleaningagent is utilized the agent is at a sufficient temperature and pressureto assume some of the solvent, surface tension and/or diffusivityproperties the agent exhibits in the supercritical state.

In particular applications of the present invention, the supercriticalfluid can have at least one surfactant and/or at least one co-solventdispersed and/or dissolved therein. For purposes of interpreting thisdisclosure and the claims that follow, the term “supercritical fluid” isutilized to refer specifically to a portion of composition that is in asupercritical state (i.e., is utilized to refer to the supercriticalcomponent of a composition). Typically, the materials dispersed and/ordissolved within the supercritical fluid will not be in a supercriticalstate and accordingly will not be part of the supercritical fluid.However, it is noted that in particular applications one or more of thematerials dispersed within a supercritical fluid can themselves be in asupercritical state. In such applications the dispersed materials thatare in the supercritical state will be part of the supercritical fluid.

The supercritical fluid can, in particular aspects of the invention,comprise one or more of CO₂, NH₃, C₃H₈, N₂O, C₂H6, CH₄, H₂O and Ar. Insome instances, the supercritical fluid can consist essentially of, orconsist of one or more of these substances. Other exemplary materialsthat can be formed into supercritical fluids which may be useful forpurposes of the present invention include an alcohol having from 1 to 5carbon atoms, for example, ethanol and/or methanol, isooctane, hexane,heptane, butane, propane, ethene, propene, dimethyl ether,tetrafluoromethane, difluoromethane, tetrafluoroethane, xenon,pentafluoroethane, sulfur hexafluoride, CFC-12, HCFC-22, HCFC-123,HFC-116, and HFC-134a.

In particular applications, a cleaning agent according to the inventioncan preferably comprise a supercritical fluid which comprises, consistessentially of, or consist of CO₂. In some applications the agent cancomprise supercritical CO₂ with various additional components or“co-agents” dispersed or dissolved therein. Such co-agents can include,for example, a co-solvent and/or a surfactant. An advantage of utilizingCO₂ as opposed to other supercritical fluids is that CO₂ has arelatively low critical temperature of about 31° C. Carbon dioxide alsohas a convenient supercritical pressure range of from about 73atmospheres (atm). Additional advantages of utilizing supercritical CO₂include its ready availability, relative non-toxicity, and lower expenseas compared to alternative solvents or cleaning technologies.

A cleaning agent consisting essentially of or consisting of a givensupercritical fluid, such as CO₂, can be utilized to dissolve certainsubstances such as, for example, many organic compounds. However, inparticular instances, it can be advantageous to increase the ability ofa particular supercritical fluid to dissolve one or more materials byutilizing a co-solvent and/or a surfactant. In particular instances, thesupercritical fluid can act as a carrier medium to carry co-solvents toareas for cleaning to occur. For example, the ability of supercriticalCO₂ to dissolve or remove ionic materials can be increased by utilizinga more polar co-solvent in conjunction with the supercritical CO₂. Anexemplary polar co-solvent can be water. Alternative solvents areavailable for use as co-solvent in conjunction with a supercriticalfluid according to methodology of the present invention as will beunderstood by those skilled in the art.

Optionally, the co-solvent/supercritical fluid mixture described abovecan additionally contain one or more surfactants. A variety ofsurfactants are available which can be utilized in the cleaning agent ofthe present invention. In particular applications, the cleaning agent ofthe invention can include a supercritical fluid combined with one ormore surfactant in the absence of any additional co-solvent. Thesupercritical fluid portion of a cleaning mixture according to theinvention can advantageously carry dispersed or dissolved co-agents intoareas that would be relatively inaccessible to liquid or conventionalsolvents.

An exemplary system 10 which can be utilized for purposes of the presentinvention is discussed with reference to FIG. 1. System 10 can be, forexample, a processing system utilized during processing of materials orduring device fabrication. System 10 can comprise a processing chamber12 used for performing one or more steps in a processing event. Chamber12 is not limited to a particular form of processing and can be achamber utilized for one or more techniques including but not limited tomaterial deposition, etching, annealing, photolithography, ionimplantation, or chemical mechanical polishing. In particularapplications, chamber 12 can be a deposition chamber utilized forprocesses including physical vapor deposition (PVD), chemical vapordeposition (CVD), atomic layer deposition (ALD), pulsed-CVD, plasmaenhanced CVD (PECVD), or high density plasma deposition (HDP). In otherinstances, chamber 12 can be a furnace chamber or other batch tool. Inparticular embodiments of the invention, system 10 can be utilized forsemiconductor processing system and chamber 12 can be a semiconductorprocessing chamber.

Chamber 12 can have various internal surfaces over which variousunwanted residue materials can be deposited during the semiconductorprocessing steps performed therein. Such internal surfaces can comprise,for example, wall surfaces 14 and/or surfaces comprised by one or moresystem components internal to chamber 12 such as a surface of a heater15, a surface of a substrate holder 16 and a surface of a disperser 18.Internal components 15, 16 and 18 are not limited to a particularconfiguration and can be, for example, any component utilized as aheater 15, as a substrate holder 16 (for example to hold one or moresemiconductor wafers) or as a disperser 18 during semiconductorprocessing. Such internal features can be integral or removable.

In addition to the internal surfaces discussed above, the inventionencompasses placement of additional processing equipment or tools intothe chamber specifically for the cleaning process. Accordingly, system10 can be utilized for cleaning within chamber 12, surfaces that werenot within chamber 12 during the deposition or other processing event.For example, a semiconductor wafer holder which held one or more wafersduring processing within an alternate processing chamber can be cleanedby placing such holder into chamber 12 during the cleaning process.

Processing system 10 can comprise, for example, a cleaning agent source20. In applications where the cleaning agent will be utilized in asupercritical phase, source 20 can comprise the supercritical fluidphase of the agent and the agent can be provided into chamber 12 throughinlet 22 in supercritical form. Alternatively, source 20 can provide thecleaning agent into chamber 12 in liquid form or gas form and a cleaningagent 20 can be converted to its supercritical phase within chamber 12.In applications where cleaning agent 20 will be utilized in a liquid ornear supercritical form, source 20 can be a liquid or can alternativelybe a gas which can be converted into a liquid by an appropriate increasein pressure within chamber 12 relative to source 20.

In applications where a co-solvent and/or a surfactant will be utilizedduring cleaning, system 10 can comprise a co-agent source 26 forproviding the co-solvent and/or surfactant. Although FIG. 1 shows system10 as comprising a single co-agent source, it is to be understood thatthe invention contemplates embodiments having two or more co-agentsources (not shown) or an absence of any co-agent source (not shown).Source 26 can provide at least one co-agent selected from the groupconsisting of co-solvents and surfactants. Exemplary co-solvents andsurfactants utilized in system 10 can be any of those agents discussedabove.

Co-agent 26 can be combined with agent 20 prior to flowing cleaningagent into chamber 12, or alternatively can be provided independently ofagent 20. Co-agent 26 can be provided through common inlet 22, as shownin FIG. 1 or alternatively can be provided through an independent inlet(not shown). When provided independently, co-agent 26 can be providedsimultaneously with agent 20, can be introduced into chamber 12 prior toagent 20, or in particular instances can be introduced subsequent toagent 20.

In some applications of the invention, co-agent 26 can be utilized as apre-treatment substance. For example, one or more co-agent can beindependently provided into chamber 12, and can contact and/or reactwith materials on surfaces internal to system 10 prior to any flowing ofagent 20. Agent 20 can then be provided within a portion or all of theinternal areas of system 10 to interact or mix with the co-agent. Themixture of agent and co-agent can subsequently be removed from theinternal areas of the system along with any materials dissolved ordispersed therein.

Whether or not cleaning agent 20 is utilized in conjunction with asurfactant and/or a co-solvent, agent 20 can be introduced into chamber12 in gas phase, in liquid phase or in supercritical fluid phase. Whereagent 20 is introduced into chamber 12 in a non-supercritical phase andwhere cleaning of chamber 12 will utilize the supercritical fluid phase,temperature and pressure conditions of chamber 12 can be provided suchthat agent 20 is converted to the supercritical phase within chamber 12.In particular instances, it can be preferable that agent 20 be flowed orinjected into chamber 12 in supercritical phase.

Processing system 10 can comprise one or more reagent inlets 24 and feedlines 25 for introduction of one or more reagents utilized duringsemiconductor processing or other processing events. As indicated inFIG. 1, inlet 24 can be configured such that one or more reagents areprovided into chamber 12 through disperser 18. Disperser 18 is notlimited to a particular type of disperser and can be, for example, ashower head type disperser. System 10 can further comprise additionalinternal features such as heater 15 and substrate holder 16. It is to beunderstood that the internal features, as well as the inlet and outletconfiguration shown in FIG. 1 represents an exemplary apparatusconfiguration. The invention additionally encompasses utilizing cleaningmethods of the present invention for processing chambers havingalternate configurations and additional or different internal features.As discussed above, chamber 12 can additionally be utilized to cleanitems that are not internal components of system 10 by placing suchitems within chamber 12 for the cleaning event.

System 10 can be configured such that the cleaning fluid introduced intochamber 12 contacts at least a portion of an internal surface of inlet24 and/or feed line 25. Additionally, in particular applications system10 can be configured such that the cleaning agent contacts at least aportion of an internal surface of exhaust outlet 30 and/or an internalsurface of exhaust line 31. In embodiments where system 10 comprisesadditional feed lines, inlets, outlets, and/or exhaust lines, the systemcan be configured such that the cleaning agent contacts at least aportion of one or more internal surfaces comprised by any of thesefeatures.

As shown in FIG. 1, system 10 can comprise a cold trap 28 forutilization during the processing function of system 10. System 10 canfurther comprise a pump 32 in fluid communication with trap 28.Conventional processing systems can utilize a cold trap to recover thevarious reactants and/or byproducts from the processing stage. Forexample, during particular depositions processing, a cold trap can beprovided to condense and/or collect one or more exhaust materials afterpassing through an exhaust line which is maintained at a sufficientlyhot temperature to inhibit condensation of material prior to reachingthe cold trap. In particular applications of the present invention,system 10 can be configured such that the cleaning agent passes intocold trap 28. In applications where the cleaning agent comprises asupercritical fluid, cold trap 28 can preferably be maintained at atemperature and a pressure sufficient to maintain the supercriticalfluid phase of the agent during cleaning.

The cleaning agent introduced into chamber 12 can pass through outlet 30and exhaust line 31 into cold trap 28 as shown in FIG. 1. Alternatively,cold trap 28 can be exposed to the cleaning agent independently fromother apparatus components by providing the agent directly through atrap feed line 29 or through multiple feed lines (not shown).Independent cleaning of trap 28 can comprise introduction of thecleaning agent into cold trap 28 can comprise separate simultaneous orsequential addition of agent 20 and optional co-agent(s), or cancomprise providing a mixture of agent 20 and one or more co-agents asdiscussed above with respect to introducing cleaning agent into chamber12.

The cleaning agent can be exhausted from cold trap 28 and can optionallybe provided to a recovery vessel 34. In embodiments where the cleaningagent comprises a supercritical fluid, it can be preferable to maintainthe supercritical phase for the duration of the existence of thecleaning agent within chamber 12 and/or cold trap 28 to minimize oravoid having materials dissolved therein fall out of solution anddeposit within the chamber and/or the cold trap. Once the cleaning agentcarrying materials dissolved from internal surfaces of chamber 12 and/orcold trap 28 reaches recovery vessel 34, the supercritical fluid can bereleased from the supercritical state to remove and or separate solutesand/or other contaminants dispersed within the cleaning agent. Thecleaning agent can optionally be separated into its components (agent(s)and co-agent(s)), each of which can optionally be recycled back tocorresponding sources 20 and 26.

In particular applications, cold trap 28 which is disposed betweenchamber 12 and pump 32 in FIG. 1 can be eliminated from system 10 (notshown). Because the cleaning methods of the present invention allowremoval of residue material from internal surfaces of tubing or lines,it can be possible to eliminate cold traps from at least someapparatuses. Accordingly, in an absence of cold trap 28 the cleaningagent can be exhausted from chamber 12 (preferably in supercriticalphase) and can be provided to recovery vessel 34 without passing througha cold trap. It is to be noted that the invention additionallyencompasses exhausting the cleaning agent from chamber 12 into 34bypassing cold trap 28, even in those systems which include the coldtrap.

Cleaning methods of the present invention can be utilized to cleaninternal surfaces of one or more components of system 10 between eachconsecutive processing event or after a number of individual events havebeen performed. Additionally, cleaning methods of the present inventioncan be combined or alternated with conventional cleaning techniques.

Cleaning of various internal surfaces of system 10 is further describedwith reference to FIGS. 2-5. Referring initially to FIG. 2, an internalsurface such as chamber wall surface 14 can be exposed to variousreactants, products, byproducts and/or contaminants during processingevents that occur within chamber 12. In particular instances, one ormore materials 36 can be deposited onto surface 14. Material 36 can beorganic material, inorganic material, or a combination of organic andinorganic materials. Exemplary substances which can be comprised bymaterial 36 include a photoresist, a metallic material, a low-kdielectric, an oxide material, a nitride material, a hydrocarbonmaterial, a carbide material, a polymer material, a chloride material, afluoride material or a hydroxide material. In particular applications,material 36 can comprise one or more of aluminum oxide, copper, acopper-comprising material, TiN, Ta₂O₅, barium strontium titanate (BST),lead zirconate titanate (PZT), strontium bismuth titanate (SBT), NH₄Cl,TiCl₄, hafnium oxide, zirconium oxide, WN_(x), W, Pt, a platinum/rhodiumalloy, ruthenium, ruthenium oxide, iridium, iridium oxide, HfN, Ta, TaN,aluminum nitride and Si_(x)N_(y), for example (where x and y are notlimited to any particular value).

Upon completion of the processing event, or alternatively aftercompletion of a series of processing events, one or more portions ofsystem 10 can be subjected to the cleaning process described above.During the cleaning process, material 36 can be contacted by thecleaning agent which can remove some or all of material 36 from surface14 as shown in FIG. 3. For chamber cleaning purposes, it can bepreferable to remove processed wafers from chamber 12 prior toinitiating the cleaning treatment. However it is to be noted thatprocessing equipment such as, for example, substrate holder 16 as shownin FIG. 1 can be retained within chamber 12 during the cleaning process.Additional processing equipment may be retained within chamber 12 or canbe introduced into chamber 12 prior to initiating the cleaning process(not shown).

As discussed above, internal surfaces of system 10 components that areexternal to chamber 12 can also be cleaned utilizing methods of thepresent invention. Referring to FIG. 4, a line 38 having an internalsurface 40 can acquire a rescue material 42 over surface 40. Line 38 canbe, for example, a feed line or an exhaust line and material 42 can beone or more of a reactant, a product, a byproduct or a contaminant ofthe processing event. Exemplary substances which can be comprised bymaterial 42 include any of those substances indicated above with respectto residue material 36. In a given system, material 42 can be the sameor can differ from material 36 shown in FIG. 2. Material 42 can becontacted with the cleaning agent during cleaning processes as describedabove. Such contact can remove some or all of material 42 from surface40 as shown in FIG. 5.

After contacting residue material with the cleaning agent of theinvention, the agent can be vented from the system as described above.It can be particularly advantageous to utilize supercritical fluids forcleaning processes according to methods of the invention due to therelative ease of removal of such supercritical fluids from the system.Conventional methods of cleaning systems equipment and/or processingchambers can typically utilize water and or other solvents that aredifficult to eliminate entirely from the system.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1-23. (canceled)
 24. A processing system comprising: a reactor having a processing chamber; a supercritical fluid source in selective fluid communication with the processing chamber and configured for selectively flowing supercritical fluid during a chamber-cleaning process; and a recovery vessel in fluid communication with the processing chamber.
 25. The processing system of claim 24 further comprising a cold-trap, wherein the system is configured to selectively flow supercritical fluid into the cold trap.
 26. The system of claim 25 wherein the cold trap is disposed in fluid receiving relation relative to the processing chamber and in fluid providing relation relative to the recovery vessel.
 27. The system of claim 24 wherein the recovery vessel is in fluid communication with the supercritical fluid source for recycling of the supercritical fluid.
 28. The system of claim 24 wherein at least some of any solutes present in the supercritical fluid are removed in the recovery vessel.
 29. The system of claim 24 wherein the processing chamber is a deposition chamber.
 30. The system of claim 29 further comprising at least one line in fluid communication with the deposition chamber, the at least one line being utilized during deposition processes and being selected from a feed line and an exhaust line, wherein the supercritical fluid passes through at least a portion of the at least one line during the chamber-cleaning process.
 31. The system of claim 24 further comprising a co-solvent source.
 32. The system of claim 31 wherein a co-solvent is introduced into the deposition chamber form the co-solvent source subsequent to initiating flow of supercritical fluid into the processing chamber.
 33. The system of claim 31 wherein a co-solvent is dispersed within the supercritical fluid prior to initiating flow of the supercritical fluid into the processing chamber.
 34. The system of claim 31 wherein a co-solvent is introduced into the processing chamber prior to initiating flow of the supercritical fluid into the processing chamber.
 35. The system of claim 24 wherein the system is a semiconductor processing system.
 36. The system of claim 24 wherein the chamber is selected from a PVD chamber, a CVD chamber, an ALD chamber, a pulsed CVD chamber, a furnace chamber and a PECVD chamber. 